<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // "use strict";
        // function user(){
        //     console.log(this);//没有严格模式就是window，有就是undefined
        // }
        // user(); //undefined


        //但是class定义的，执行是自动加上"use strict""
        class user{
            show(){
                console.log(this);
            }
          
        }
        let u= new user();
        u.show();

    </script>
</body>
</html>